Biodegradable Methane Sulfonic Acid-Based Nonaqueous Dissolution, Estimation, and Recovery: Toward Development of a Simplified Scheme for Plutonium-Bearing Fuel Matrices

Abstract

Designing actinide separation methodologies, which simplify process scheme and minimize radioactive waste generation, form the crux for enhancing the sustainability of the nuclear industry. The present study is a step toward development of a universal and simplified scheme for the bulk assay of plutonium and uranium as a part of chemical quality control of plutonium-bearing fuel matrices. Dissolution, estimation, and recovery form the key steps for the same. Plutonium oxide, plutonium−uranium mixed oxide, and plutonium−uranium mixed carbide were quantitatively dissolved in the biodegradable organic acid, viz., methane sulfonic acid (MSA), by heating under an infrared lamp. Usage of corrosive hydrofluoric acid or refluxing conditions were avoided. Stabilization of a single oxidation state, viz., +(IV) and +(VI) for plutonium and uranium in MSA, respectively, was confirmed by ultraviolet−visible spectrophotometry and electrometry. Electrometric studies also exhibited sharp and well separated reduction peaks for U and Pu in MSA, revealing promising possibility of simultaneous voltammetric determination of U and Pu on commercially available glassy carbon electrode. The redox energetic diffusion coefficient (D 0 ) and heterogenous electron transfer kinetic parameters (αn and k 0 ) of this novel system, viz., U and Pu in MSA, were obtained using cyclic voltammetry. Single stage recovery by oxalate precipitation yielding Pu removal of >98% was also demonstrated. The findings reported herein reveal the scope for prospective applications in the front end as well as back end of the nuclear fuel cycle.